Electroslag remelting process

Claim 1

A process for producing hollow metal articles by electro-slag remelting comprising the steps of providing a metal mold of a short length which consists of an inner mold member and an outer mold member, the space defined between the mold members being composed of three vertically contiguous zones, an upper annular zone with a funnel-shaped vertical cross-section which has at the lower end portion the horizontal cross-sectional shape and size of the product being produced and is expanded upwardly therefrom, a middle annular zone with a rectangular vertical cross-section adjoining the lower end of the upper annular zone and which has the horizontal cross-sectional shape and size of the product being formed, and a lower annular zone with a trapezoidal vertical cross-section adjoining the lower end of the middle annular zone and which has at the upper end portion the horizontal cross-sectional shape and size of the product being produced and is expanded downwardly therefrom; disposing a plurality of rod-like consumable metal electrodes of a size in horizontal cross-section to approximate the horizontal cross-sectional shape of the hollow metal article being formed, said electrodes depending into said upper annular zone; inserting a starting piece having the same horizontal cross-sectional shape and size as that of the hollow metal article being formed, from the lower end of the mold up to the upper end of the middle annular zone; connecting the lower end of the starting piece thus inserted to withdrawal means located below the mold; pouring molten slag into the upper annular zoNe; supplying electric power from an electro-slag remelting power source respectively to said plurality of electrodes and the starting piece thereby producing an electro-slag remelting phenomenon therebetween; feeding said electrodes from above continuously at a controlled rate so that the electrodes continuously melt at the lower end and the molten metal drops through the molten slag to form a molten metal pool on the starting piece; allowing the molten slag to flow down and form a slag coating in gaps which are formed between the molten metal pool and the inner and outer mold members due to contraction of the metal by the cooling effect of said mold members; continuously withdrawing the starting piece together with the metal article formed thereon from the lower end of the mold, using the slag coating as lubricant at a suitable rate so that the molten metal pool can be always maintained in the upper portion of the middle annular zone of the mold, thereby forming a hollow metal article of a desired length.